<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      const user = {
        name: "jack",
        age: 20,
        birth: "2001-12-06",
        allow: true,
      };

      const r = JSON.stringify(user, function (k, v) {
        switch (true) {
          case k === "age":
            return v + "岁";
          case k === "birth":
            return v.split("-").join("/");
          default:
            return v;
        }
      });
      console.log(r);
    </script>
  </body>
</html>
